Synthesis, properties and thermal decomposition of the Ta₄AlC₃ MAX phase

The present work describes a synthesis route for bulk Ta ₄ AlC ₃ MAX phase ceramics with high phase purity. Pressure-assisted densification was achieved by both hot pressing and spark plasma sintering of Ta ₂ H, Al and C powder mixtures in the 1200–1650 °C range. The phases present and microstructures were characterized as a function of the sintering temperature by X-ray diffraction and scanning electron microscopy. High-purity α-Ta ₄ AlC ₃ was obtained by hot pressing at 1500 °C for 30 min at 30 MPa. The β-Ta ₄ AlC ₃ allotrope was observed in the samples produced by SPS. The Young's modulus, Vickers hardness, flexural strength and single-edge V-notch beam fracture toughness of the high-purity bulk sample were determined. The thermal decomposition of Ta ₄ AlC ₃ into TaC _x and Al vapour in high (˜10 ⁻⁵ mbar) vacuum at 1200 °C and 1250 °C was also investigated, as a possible processing route to produce porous TaC _x components.